1. Field of the Invention
The present invention relates to a photosensitive resin composition having photocurability, thermosetting property, and developability with water or a diluted alkali aqueous solution, which can be preferably used as a photosolder resist ink to manufacture printed wiring boards.
2. Disclosure of the Prior Art
In the past, the screen-printing method has been mainly utilized to form solder resist films on printed wiring boards. However, as excellent resolution and tightly restricted dimensional tolerances are needed in recent years, the demand for liquid-type photosolder resist inks increases in place of the screen-printing method. For example, as disclosed in Japanese Patent Early Publication No. 61-243869, No. 2-173747, No. 7-72624, or No. 9-235348, there is a photo solder resist ink including a polyfunctional epoxy compound and an ultraviolet-curable resin obtained by adding an unsaturated group and carboxyl group to a novolac-type epoxy resin or an acrylic copolymer, which is developable with a diluted alkali aqueous solution.
However, in this kind of photoresist ink, ink components are dissolved or dispersed in an organic solvent to uniformly apply the ink components on a substrate. Therefore, it is generally required to evaporate the organic solvent from the photoresist ink by predrying prior to the subsequent exposure step. Thus, when using such a photoresist ink, there are problems inherent in the use of organic solvent, for example, a poor working condition, environmental pollution and the occurrence of a fire.